1. Technical Field
The present invention generally relates to a digester method and system for processing farm and other agricultural/industrial waste. More particularly, the present invention provides a method and system for processing farm waste using a small-scale digester that receives and processes only a small portion of a raw waste stream, thereby inducing greater anaerobic decomposition in an existing waste storage structure.
2. Background Art
On farms, processing waste is a problematic issue. In particular, not only can farm/animal waste cause foul odors, but also can cause water contamination from disease causing organisms released to the surrounding environment. Moreover, should waste be released to the environment surface and ground water supplies could become polluted and harm aquatic organisms. To address these problems, farmers commonly utilize digesters to help process and decompose the waste. The digesters can also be used to capture methane gas, which can later be used as a fuel source for the farm. Accordingly, digesters not only serve to reduce problems attributable to farm waste, but also help provide a fuel source for the farm.
In a common implementation, raw farm waste is gathered in a collection system such as a trench, tank, etc. The entire raw waste stream is then passed to a digester. Once in the digester, the raw waste stream is processed over several days or weeks. During anaerobic digestion, microorganism populations grow as they decompose the waste material. These microorganism populations produce gases such as methane. The gases can be collected from the digester and fed to a generation system to provide power to the farm. Once the waste has been completely processed, the waste stream is then fed to a waste lagoon where the bacteria created during digestion will decompose the waste.
Heretofore, many have attempted to provide improved digesters to more efficiently process the farm waste and harness the gasses produced therefrom. However, to process the entire waste stream, such digesters must be constructed on a large scale. For example, a 1000 cow dairy farm could require a digester with a capacity in excess of 300,000 gallons to process 100% of the waste generated. These large-scale digesters are not only expensive to produce and maintain, but also require a large storage space. In addition, large-scale digesters recover methane only within the digester itself, as opposed to within the waste lagoon. Because the lagoon can be significantly larger than the digester, this limits the total methane that can be recovered. Accordingly, a more productive methane recover operation would be to recover the methane in the lagoon using a lagoon cover or the like.
Accordingly, there exists a need for a digester that does not require large dimensions. In addition, there exists a need for such a digester that need only treat a small portion of a raw waste stream. There also exists a need for a digester that causes methane production to occur in the waste lagoon, as opposed to in the digester. There also exists a need for an less expensive way to control odors and recover methane.
The present invention overcomes the problems associated with existing systems by providing a small-scale digester method and system. The digester of the present invention requires that only a portion of the raw waste stream be treated. Moreover, the digester of the present invention causes substantially all methane production and anaerobic decomposition to occur in the lagoon.
According to a first aspect of the present invention, a method for digesting waste is provided. The method comprises: (1) providing a digester; (2) directing only approximately 0.1% to 10% of a raw waste stream into the digester; and (3) processing the directed waste stream in the digester.
According to a second aspect of the present invention, a digester is provided. The digester comprises: (1) an inlet for receiving a maximum of approximately 0.1% to 10% of a raw waste stream; (2) a processing tank for processing the received raw waste stream; and (3) at least one outlet for feeding the processed waste stream to a lagoon.
According to a third aspect of the present invention, a digester system is provided. The system comprises: (1) a storage system for storing a raw waste stream; (2) a digester comprising an inlet, a processing tank and at least one outlet, wherein only approximately 0.1% to 10% of the raw waste stream is received from the storage system by the inlet and processed in the processing tank; and (3) wherein the processed raw waste stream is fed through the at least one outlet to a lagoon.
Accordingly a small-scale digester is provided that need only treat approximately 0.1% to 10% of a raw waste stream. The digester of the present invention reduces construction, installation and maintenance costs and allows substantially all methane production to occur in the waste lagoon.
The preferred embodiment of the present invention is designed to solve the problems herein described and other problems not discussed, which are discoverable by a skilled artisan.